LEWISTON — Authorities continued Friday to interview witnesses and review surveillance video in an effort to narrow their search for suspects in a rash of fires on April 10 in the city’s downtown.

Investigators have interviewed more than 40 people of interest during their canvass of the area in the wake of four arsons and one attempted arson on that day.

Police Chief Michael Bussiere said area businesses have cooperated with investigators by turning over private surveillance of the area beginning hours before the first fire was detected at about 1 a.m. that day.

In addition to private video, investigators have reviewed hours of footage from cameras on light poles, traffic signals and other public utilities.

Meanwhile, fire investigators said all of the properties involved were listed as insured except for 21-23 Howe St., which has a single owner. The insurance policy on those buildings, which had a combined assessed value of $168,900, had lapsed, and they were uninsured at the time of the fires, fire Chief Paul LeClair said. The insurance company had notified the mortgage holder, who, in turn, notified the owner of the lapse, Inspector Paul Ouellette said.

A building at 44 Nichols St., which also sustained heavy fire damage, was insured and owned by a bank and had been condemned and vacated.

Fires at 48 Howe St. and 135 Oxford St. caused minor damage. A fire was attempted at 61 River St.