One man wounded in a bus bombing in southern Jerusalem Monday remained in life-threatening condition a day later, while 11 others were still hospitalized.

Police had yet to identify the man who was seriously injured in the blast and were investigating the possibility that he was the bomber, a spokesperson said.

However, she said, “All of the details and circumstances are still being checked and investigated.”

A Jerusalem court put the details of the investigation and the identities of suspects under a gag order.

The man suffered severe burns and extensive injuries to the limbs, according to Shaare Zedek Medical Center, where he is being treated.

Firefighters and rescue personnel at the scene of a bus bombing in Jerusalem, on April 18, 2016, leaving at least 21 people injured. (Nati Shohat/FLash90)

Firefighters and rescue personnel at the scene of a bus bombing in Jerusalem, on April 18, 2016, leaving at least 21 people injured. (Nati Shohat/FLash90)

He underwent surgery on Monday night, and was unconscious and intubated in the Jerusalem hospital’s intensive care unit on Tuesday morning, the medical center’s spokesperson Shoham Rubio said.

“He is in unstable and life-threatening condition,” she said.

He was apparently closest to the blast, which accounted for both the severity of his injuries and the police suspicion that the attack was an attempted suicide bombing.

The 21 victims of the bombing were taken to three hospitals in the capital on Monday, but 11 of them were quickly released home.

Eden Dadon, a 15-year-old resident of Jerusalem, also remained unconscious and intubated in moderate condition on Tuesday morning, her mother Racheli said.

The two had been riding the bus together at the time of the attack.

“Everything was dark and smoky. I looked for my daughter and she was all burned,” Racheli Dadon told reporters. “After the explosion I collapsed. Her face was all black, you couldn’t see her.”

Two moderately injured victims who underwent surgery remained in Shaare Zedek Medical Center, though they were stable, conscious and capable of breathing on their own, Rubio said.

Three lightly wounded victims also stayed in the hospital through Tuesday morning, she added.

In Hadassah Hospital in Ein Kerem, six victims were still being treated. Four of them were in moderate condition, and the other two lightly injured.

Firefighters look on as two buses burn in Jerusalem. Police launched an investigation into the incident, April 18, 2016. (Israel Police)

Firefighters look on as two buses burn in Jerusalem. Police launched an investigation into the incident, April 18, 2016. (Israel Police)

The number 12 bus exploded on Moshe Baram Street in the Talpiot neighborhood of the capital at approximately 5:45 p.m., also setting another bus and a passing car on fire.

There was uncertainty at first over whether the explosion was the result of a terror attack or a mechanical malfunction. After a preliminary investigation, Jerusalem Police Chief Yoram Halevy confirmed the blast was caused by a small explosive device, apparently placed in the back portion of the bus.

“When a bomb explodes on a bus, it is a terror attack,” Halevy said, adding it was unclear if the bomber had been on the bus at the time of the blast.

The terror attack broke weeks of relative calm in the city after a six-month wave of Palestinian stabbings, shootings and vehicular attacks seemed to be subsiding, and raised fears of a return to a type of violence not seen in Jerusalem for years. The second intifada terror wave between 2000 and 2005 saw Jerusalem frequently targeted by suicide bombers on buses and in restaurants.

There was no immediate claim of responsibility for the blast by any terrorist groups or individuals, though several Palestinian terror groups praised the bombing in statements.

Prime Minister Benjamin Netanyahu, speaking Monday night, said Israel would “settle the score” with those responsible for the bombing.

Times of Israel staff contributed to this report.