The April 27 fire at the Crystal Airport may have been caused by disregard for Metropolitan Airports Commission rules that require hangar space be used primarily for airplanes and not ground vehicles. The fire destroyed four planes, a truck and a few motorcycles.

A commercial-size truck that apparently started the blaze shouldn't have been in the hangar to begin with, said MAC officials. Last week, officials inspected 100 stalls owned by Bruce Wiley, who owns the hangar that burned and is on land leased from the airport.

The MAC inspection found that five stalls contained 11 cars, two boats and household items, in violation of MAC rules.

Brooklyn Park fire officials have said the fire likely started when the truck, which was being worked on in a rented stall in Hangar CF, backfired about 11:45 a.m. A man working on the truck was slightly burned and the hangar was damaged badly enough that it will have to be torn down.

The man working on the truck was subletting the stall from the original renter without Wiley's knowledge, MAC officials said. The renter has been evicted.

The other stalls found in violation were rented by three individuals, said Gary Schmidt, MAC's director of reliever airports. Wiley had 10 days to correct the violations, MAC officials said.