The church's stage area seen on Saturday after the collapse. (CBC)

More than 40 people were taken to hospital — three with serious injuries — after the floor caved in at a packed concert in an Abbotsford, B.C, church late Friday night.

"We were dancing in the front of the stage," Kyle Weber, a teenager who was at the Christian rock concert, told CBC News. "The floor just collapsed. All the speakers just fell down [and] crashed a lot of people.... A lot of people fell through the floor."

At least 23 people were sent to MSA Hospital in Abbotsford, while 16 people were diverted to nearby hospitals in Mission, Chilliwack and Langley, local health officials told CBC News late Friday night. Two more were taken to Vancouver General Hospital.

Police in the Fraser Valley community said they didn't know how many people were actually hurt in the incident at Central Heights Church, but they confirmed that at least three people were hospitalized with serious injuries.

A teenager was taken away by a stretcher outside Central Heights Church after its floor caved in late Friday night during a packed rock concert. (CBC)

Karen Thiessen and her eight-year-old-son were at the concert when "the heavy lights above the auditorium started to fall towards the crowd" at about 9 p.m., she told CBC News.

A mosh pit in front of the stage was filled with teenagers, she said, and they were jumping and dancing. After the lighting fell, the floor beneath the mosh pit collapsed, she said, and the people on it fell through to the basement about three metres below.

About 1,200 people were watching the concert at the church, at 1661 McCallum Road, she said.

The sold-out event featured contemporary Christian rock band Starfield. A couple of warm-up bands were playing their music when the accident happened, Thiessen said.

Several concert-goers — most of whom were teenagers — were cared for by paramedics at the scene, Thiessen said. She and her son, Isaac, were not hurt.

Ian Hern, a youth pastor at the concert, said there were hundreds of youth jumping and dancing at the time.

"All of a sudden, one of the light poles started to tilt and then the whole floor just caved," Hern said.

Some of the young members in his group suffered injuries such as a broken arm or a dislocated shoulder, Hern said.

"Obviously, the church floor wasn't built to handle that number of people," Hern said.

RCMP from the nearby communities of Langley and Mission were called in to assist the Abbotsford police.

Extra doctors and nurses were also brought in to help paramedics treat the injured, police said.