At least three of the 14 people injured after an explosion and fire at a three-story building in Minneapolis remain in critical condition Thursday.

Authorities aren’t sure whether any residents are still inside the building but no fatalities had been reported as of Thursday morning.

The structure’s roof had partially collapsed, making it too dangerous for firefighters to enter.

One neighborhood resident watched the blaze from the third floor of a Riverside Plaza apartment building, where he could see the back of the burning building, which housed a grocery story and apartments above. Barry Peterson, 51, said the roof of the building collapsed about 10:45 a.m.

“We just saw a lot of fire and then a lot of smoke,” he said, adding that the blazes were “steady.”

Crews didn’t know how many people were in the brick structure when fire broke out about 8:15 a.m., Minneapolis Fire Chief John Fruetel said.

The cause of the explosion and fire was under investigation Wednesday as inspectors examined the charred, ice-coated buildind, Fruetel said.

The building at 516 Cedar Ave., which is next door to the Masjid Dar Al-Hijrah mosque and in the same block as Palmer’s Bar, is believed to be a total loss. Crews fear it could collapse, Fruetel said.

The building was last inspected in 2012 and had no outstanding inspection issues, according to the fire department.

Farah Ahmed said his brother, his uncle and his friends own Otanga Grocery, the business in the ruined first floor.

“(The grocery store) was a center of communication. It was a center of gathering,” Ahmed said at the news conference. “We came from East Africa and we made it. We did start from scratch and we will make it again, with your support.”

Mubashir Jeilani, a nephew of three of the store’s owners who lives in an apartment nearby, said the grocery store was more than a business; it was a “connected market.”

“People had tabs there,” the 18-year-old said. “People came there to socialize.”

As police reported the fire, an officer could be heard saying that people were jumping from second-floor windows and that injured people were gathering outside.

“It’s not clear whether people were pushed out of the building from the explosion or whether they fell or jumped out of windows to escape,” said Robert Ball, a spokesman for Hennepin County Emergency Medical Services.

Ten people, including the three in critical condition, were being treated Wednesday at Hennepin County Medical Center. One person had been released Thursday.

Hospital spokeswoman Christine Hill said all were suffering from burns, broken bones or both.

Fruetel said flames were shooting as high as 20 feet from the windows of the building’s second and third floors when fire crews arrived.

More than 50 firefighters were on the scene throughout the day, according to the fire department.

When firefighters arrived, heavy smoke and flames were shooting from the second and third floors of the building, the fire department said. Several injured people who had escaped the burning building were standing outside.

Firefighters rescued people from the building and fought the blaze inside the first floor until they had to evacuate because fear the building would collapse, the news release said. The release said a second alarm was called at 8:22 a.m. and a third at 8:33 a.m.

Roughly 90 minutes after the explosion, smoke clouded the neighborhood and a nearby stretch of Interstate 94.

No firefighters were injured.

Temperatures of about 10 below hindered firefighting efforts. It was difficult to draw water from fire hydrants and crews had to quickly transition from frigid weather to significant heat closer to the blaze.

“I know we’ve had a number of trips and falls but no reported injuries (to firefighters), which is remarkable,” Fruetel said.

Mist and water from the fire hoses coated the building, the crews’ ladders and nearby trees. Large tree branches became thick with ice and fell onto Cedar Avenue.

By 11:30 a.m., it appeared that active efforts to control the fire had largely concluded, although firefighters still couldn’t enter the building Wednesday afternoon because of heat, smoke and possible structural damage.

By 5 p.m. the building resembled a charred icicle; smoke billowed from the roof and a mural on the south side of the building was coated in ice.

An American Red Cross disaster team captain said the organization was helping people at the hospitals as well as residents who were not home at the time of the disaster. He said they were providing victims with temporary housing, food and clothing as needed.

Mayor R.T. Rybak and Mayor-elect Betsy Hodges visited the scene Wednesday morning and spoke at the news conference in the afternoon.

“This is a community that’s been through a lot,” Rybak said. “People who come to live in this part of our city often have gone through horrendous things. They come here for peace and for safety. It’s especially tragic to think that people who have come through so much now have to go through even more.”

“I know that all the folks in the city of Minneapolis are ready and waiting and willing to come together to help the folks that have been affected by this tragedy,” Hodges said.

Abdisalam Adam, board chair of the Islamic Civic Society of America, which operates the mosque, said the building sustained only water damage and had lost its electricity. He said he is concerned about the building’s water pipes freezing. Until the building passes inspection, mosque services would take place at the Brian Coyle neighborhood center.

The Salvation Army Northern Division was working with first responders at the-scene and tweeted that it was “preparing to serve families as needed.”

Nick Woltman and C.J. Sinner contributed to this report.

This story contains information from the Associated Press.