jrodriguez@mercurynews.com

REDWOOD CITY -- Twenty-one people, including three firefighters, were injured in a six-alarm fire early Sunday that also forced 97 tenants out of their apartments and closed Woodside Road for most of the day. None of the victims were seriously burned or injured.

City officials said the fire started shortly before 2 a.m. at the four-story Hallmark House apartment building at 531 Woodside Road. The first of 100 firefighters to arrive found desperate apartment tenants standing on their balconies pleading to be rescued.

Firefighters climbed seven ladder trucks to bring victims down safely and then used equipment from 20 engine trucks to bring the blaze under control. The fire burned so hot it was still smoldering and considered active at 9:30 a.m.

Redwood City spokesman Malcolm Smith said firefighters would remain at the site overnight to guard against a flare-up. Because of that danger, he said, an investigation into what started the fire will not begin until Monday morning.

The Red Cross and city officials set up an overnight shelter at the National Guard Armory on Velota Road for about 40 residents who had nowhere to go. Volunteers and Red Cross staff offered prescription medicine replacement and emotional support.

Most of the 21 people taken to local hospitals suffered minor to moderate injuries and were expected to be released Sunday. Woodside Road was closed in both directions from Bonita Avenue to Hess Avenue.

Contact Joe Rodriguez at 408-920-5767. Follow him at Twitter.com/JoeRodMercury.