Investigators were working yesterday to find the cause of a two-alarm fire Monday night in the Hill District.

The fire was reported at 10:11 p.m. in a row house in the 2300 block of Ridgeway Street.

The blaze spread to an abandoned unit next to the occupied one.

No injuries were reported.

Only one resident, an elderly man whose name was not released by city fire officials, was forced out of the dwelling.

Damage is estimated at $36,000.