HOUSTON -

Houston police use emergency road flares to alert drivers to hazards on the road. Now, there is mounting evidence these pyrotechnics may pose a hidden danger to officers, possibly because of how they're being stored in the trunks of police cruisers.

"Our officers said they just went through the parking lot over a speed bump and after that, within minutes, I noticed some fumes coming from the trunk," HPD Assistant Chief M. Curran said.

Local 2 has learned that HPD has lost five patrol cars to trunk fires over the past two years. While there are no reports of officers being injured, department officials are so concerned they've asked the Houston Fire Department and the National Transportation Safety Board to investigate.

Police said the flares are very easy to light because of the chemicals that are used. Over time, the trunks where they are stored get so hot because of the Houston heat. That can cause the tape that binds them to break down and peel off.  Right now, officers use plastic containers to secure and store the flares but HPD is considering switching to metal bins.

Meantime, the department recently issued a memo urging the rank and file to routinely inspect the flares to make sure they are intact.

"If we vacuum seal the flares it may be another way to keep them from moving about," said Chief Curran.

Electronic flares may be another option for HPD to explore, but police say right now they're not cost effective.