The uncle of the 19-year-old suspect in the Boston Marathon bombings urged his nephew to turn himself in and seek forgiveness.
"If you are alive, turn yourself in and ask for forgiveness," Ruslan Tsarni told reporters outside his home in Maryland. "Turn yourself in."
Boston and its suburbs, universities and transit system were on lockdown Friday as police hunted for Boston Marathon bombings  suspect Dzhokhar Tsarnaev, still at large after his accomplice brother, Tamerlan Tsarnaev, 26, was killed in a series of events that left an Massachusetts Institute of Technology police officer dead and a transit officer injured, officials said. Three people died and more than 170 people were injured in the Monday blasts.
Boston Police posted on its Twitter page: "Police seeking MA Plate: 116-GC7, '99 Honda Sedan, Color - Green. Possible suspect car. Do not approach."
The Connecticut State Police said on its website it received information from Boston officials "that a suspect vehicle could POSSIBLY be occupied by a wanted suspect."
Massachusetts State Police Col. Timothy Alben said there would be a "controlled explosion" in one neighborhood being searched in Cambridge where the two brothers lived.
"It's done out of an abundance of caution" before police search the premises, he said.
He did not say whether explosives had been found.
Saying he had been following events, Tsarni said, "I never, ever would have imagined that somehow that somehow that the children of my brother would be associated with that."
Asked about a possible reason, the uncle said, they were "losers" for bringing about the atrocity and they apparently had a "hatred for those who were able to settle themselves."
If he had known, he would have called police, Tsarni said, adding later that he would consider them terrorists.
Anything to suggest the brothers' actions were motivated by Islam "is a fraud and a fake," he said.
Tsarni, who said his family was ethnic Chechen and Muslim, said his nephews "put a shame on our family. He put a shame on entire Chechen ethnicity."
NBC News reported counterterrorism officials were looking into the possibility the Tsarnaev brothers were linked to the Islamic Jihad Union of central Asia, a terrorist group.
NBC New York said it has obtained travel records indicating Tamerlan Tsarnaev went to Russia from Jan. 12-July 17, 2012.
After their photos were released by the FBI Thursday, the brothers carjacked a Mercedes SUV and told the driver they were behind Monday's attack and had just killed a campus security officer, a source told NBC News. The driver was released unhurt.
The older brother, Tamerlan Tsarnaev, was killed after a chase and gunfight.
Dzhokhar Tsarnaev remained at large and police said they believed he was hiding out in a densely populated area in Watertown.
Police said they believe Dzhokhar Tsarnaev has a laptop and was communicating via social media, CNN reported.
In a brief conference with reporters, a Boston police official said there was another possible suspect who was "not suspect no. 2" as Dzhokhar Tsarnaev is identified in the photo released by the FBI.
The official said police have found a 1998 Honda CR-V that was present at the time of the carjacking and one suspect drove it away. The official said he didn't know whether the CR-V had been stolen or if the suspects owned it.
Boston Logan International Airport said on its website it was open and "operating under heightened security. Please check with your airline on flight status before heading to the airport."
Massachusetts Gov. Deval Patrick and Boston Mayor Tom Menino urged residents to remain indoors until an all-clear is given.
"Please keep your doors locked unless there's a uniformed identified law enforcement officer on the other side," Patrick said.
Police said those who went to work Friday morning weren't expected to remain there.
"Workers encouraged to return home," a post on the Boston police Twitter page said .
President Barack Obama has been briefed on the situation throughout the night and day, the White House said.
The Boston Globe said it was told by a law enforcement source an explosive trigger was found on Tamerlan Tsarnaev's body at the morgue. It had been reported he had explosives on his body when he was killed.
Transit and Amtrak service were suspended in Boston and its suburbs. Taxi service, which was initially suspended, was restored late morning. Colleges and universities canceled classes. Residents were told to stay indoors and businesses were told not to open.
The Boston Bruins canceled the team's morning skate.
The Boston Red Sox posted on their website: "The Boston metropolitan area was locked down Friday as authorities pursued a second suspect in Monday's Marathon attacks, which has put the status of tonight's Royals-Red Sox game in question."
MIT police officer Sean Collier, 26, of Somerville, was killed and Boston area transit police officer Richard H. Donahue Jr. was critically wounded when the brothers carjacked a vehicle. WBZ, Boston, reported Donahue was out of surgery Friday afternoon and in stable condition.
Ten officers were being evaluated at St. Elizabeth's Medical Center in Brighton for injuries sustained from grenades thrown from the window of a car during a chase, the Globe said. No further information was available.
WBZ reported the men were permanent U.S. residents. WBZ said the younger brother became a U.S. citizen in September and was a student at the University of Massachusetts-Dartmouth.
Tamerlan Tsarnaev was a competitive boxer and his brother was on the wrestling team in high school.
Neighbors of the younger brother described him as strange but said they could not articulate what made them say that, WBZ reported.
ABC News reported police said they believed the surviving suspect has assault rifles and other weapons, possibly including bombs.
ABC News said they may have been trained in Turkey, but their uncle said they did not have military training.