[Update 7:15 p.m.]
At about 6:30 p.m. fire personnel turned off the truck hoses and began inspecting the inside of the building. No flames or new smoke could be seen emerging from the structure.
Lt. Peter Penenate, who also works in the fire inspection department, confirmed to Patch that there were no serious injuries. One resident, he said, was evaluated for heat.
Penenate said at this time the cause of the fire is unknown and an investigation will be undertaken. He said the cause may be known and information on it available by tomorrow at the earliest.
Prospect Street was still closed off to all traffic but Montvale Avenue had been reopened.
The residents are being assisted by the American Red Cross, according to Kat Powers, director of communications at the American Red Cross of Eastern Massachusetts. She said the Red Cross has been told by Woburn Fire there are three families in need of assistance.
[Update: 5:55 P.M.] NStar is now on the scene at the fire on Prospect Street after fear of fire sparking neighborhood electrical lines.
[Update 5:46 p.m.] Fire at the house on Prospect Street has sparked electrical lines; police are trying to get everyone in the large gathered crowd off the street and away from the house.
[Update 5:32 p.m.] Prospect Street neighbors say it was kids from the neighborhood who first saw the fire this afternoon at 6 1/2 Prospect Street in Woburn.
They told their parents and the parents called 911.
The kids ran to tell adults and Nicole Ortiz and another woman immediately called 911. Then, said Ortiz, they started banging on the doors of the house to warn the residents of the house on Prospect Street. She said one uninjured man walked out by himself after she banged on the door.
"The kids were the ones who saw the smoke and came running to tell us," Ortiz told Patch editor Richard Hosford. When she arrived, it was mostly at the back of what appears to be a two-story-plus-attic vinyl-clad building, but spread quickly.
Oritz estimates it took the fire department 5-10 minues to arrive.
There is now less smoke and flames than there was 20 minutes ago, when firefighters cut two holes in the building roof and flames shot out.
Montvale avenue closed at main street. police on scene directing traffic.
Witnesses said they did not see anyone taken away in ambulances. And while firefighters are not trying to get into the building, Hosford saw a firefighter poke his head out of a second-story window about 20- minutes ago.
Firefighters from Woburn, Winchester, Burlington and now Arlington Fire Departments have responded to the two-alarm blaze, along with Woburn Auxiliary Fire and Rescue. Eight trucks are still on the scene, and two water hoses are still trained on the attic.
Interesting note: the kids who reported the fire told Hosford that they saw a cat jump out of the house window early on in the fire.
Original report: Emergency scanners and Twitter are showing reports of a fire in the third floor and attic of a Prospect Street home.
Woburn, Winchester and Burlington Fire Departments are responding to the incident.
Reports indicate there is heavy traffic in the area that are causing delays.
Patch will bring further updates as more information becomes available.