A BUSY FRANKFORD intersection will be closed indefinitely as crews repair damage from a massive water-main break yesterday that forced dozens of schools to close.

The Philadelphia Water Department said it detected a break in a 48-inch cast-iron pipe about 8:50 a.m. at Frankford and Torresdale avenues. The break caused low water pressure in various sections of North Philadelphia and Fairmount.

A day-care center and six residents near the intersection were temporarily evacuated, officials said. The low pressure also forced the School District of Philadelphia to dismiss 37 schools at 11:30 a.m.

Water pressure was restored to the affected areas by 2:30 p.m., the Water Department said.

"The street will be out for a while," Mayor Nutter said at a news conference near the site. "There's a lot of work to be done. The main is 20 feet down in the ground."

Winter break for the city's public schools begins today, but yesterday's abrupt dismissal was a surprise for parents, many of whom had to scramble to pick up children.

Fairmount resident Gili Ronen, who works from home, picked up two of her children and a neighbor's child from Bache-Martin Elementary, at 22nd and Brown streets.

"It was actually OK for me. I would imagine for people who were at work it was an inconvenience," Ronen said as her children splashed in rain puddles outside their Fairmount school.

Water Department Commissioner Howard Neukrug said officials did not yet know what caused the rupture of the pipe - which dates back to 1907. He said that because of the pipe's depth, there were no issues with freezing and thawing.

"We'll look into it and see whether age is a factor," he said.

Crews will work to clean up the site, at which point claims adjusters and inspectors will survey the damage before repairs are ultimately made, Neukrug said.

A Fire Department official said that during its peak, the water was 3 to 5 feet deep near the ruptured main.