A small explosion that damaged a sidewalk in the heart of downtown Portland on Sunday appears to have been an issue with an underground electrical vault, according to a fire department official.

The Portland Fire Department responded around 1 p.m. to an area near the intersection of Exchange and Middle streets for a report of an electrical vault explosion on the sidewalk, fire department spokesperson Sean Donaghue said Monday.

Crews arriving on scene found a manhole cover and a roughly 4-by-4-foot area of the surrounding sidewalk damaged. No active fire was present at the time, and the explosion appears to have been related to an electrical vault issue, Donaghue said. No injuries were reported.

The fire department checked the basements of surrounding buildings for damage and any presence of natural gas and carbon monoxide but found no significant issues.

Central Maine Power was called to the scene to further assess the issue, Donaghue said.

A written statement from CMP Monday said the utility is continuing to investigate the incident. “Our crews immediately responded to make our lines and the site safe and no customers were without power related to this incident,” the statement said.