Police say thieves have come up with a new way to steal fuel from local gas stations.

Thieves are parking on top of underground fuel tanks, removing the cap, dropping a hose down and using a pump to siphon fuel.

On Sunday and Monday mornings, thieves stole diesel fuel from three Speedway stations in Porter County -- getting 100 gallons from the one on Gateway Boulevard in Chesterton; 177 gallons from the one at U.S. 6 and Swanson Road in Portage; and 175 gallons from the one west of Valparaiso at U.S. 30 and County Road 475 West.

"I'm working with Portage and county police right now to get all the (surveillance) video together, but it looks like they are related in some fashion," Chesterton police Lt. David Cincoski said.

Cincoski said the theft spree shows the need for gas stations to better secure their underground tanks, to make sure they have video cameras trained on the tanks and to watch for suspicious vehicles parking on top of the tanks.

At Speedway, the underground tanks have "rapid loss alarms" that activate if a certain amount of fuel disappears without being pumped. Cincoski said he encourages clerks to call police immediately if they see suspicious activity or if an alarm activates.

At the Union Township Speedway station, surveillance video shows a two-tone Chevrolet truck parking over the tank. A second truck, which appears to be a red Dodge with two silver tool boxes mounted in the truck bed, parked between the store and the Chevrolet truck -- perhaps to block the view, Porter County police Maj. Steve Lawrence said. A person raised the hood of the Dodge truck and appeared to be working on the truck.

At the Chesterton Speedway station, surveillance video shows a single pickup truck parked over the fuel tanks.

At the Portage Speedway station, surveillance video shows a red pickup truck and a dark pickup truck.

The thieves, who take 15 to 20 minutes to steal the fuel, apparently have some type of bladder or tank in which they put the fuel. Police said there were a few other similar thefts in Porter County before this recent spree.

Police are releasing surveillance photos, and they are encouraging anyone with information to call Chesterton police at (219) 926-1136; county police at (219) 477-3000; or Portage police at (219) 762-3122.