WINDHAM — A Westbrook tinkerer found himself in hot water Monday as his plan to build his own pontoon boat turned into a weapons-of-mass-destruction alert for local emergency responders.

Joshua Prokey, 30, an electrician, was driving north on River Road at 9:40 a.m., eager to work on the project he’s been dabbling with for close to five years. He planned to add more than a dozen 120-gallon propane tanks for flotation.

By the afternoon, he was in Cumberland County Jail – but not for terrorizing, or even poor handling of hazardous materials. It turns out one of his propane tanks – the one he was using to power his modified van – was stolen, police said.

Prokey was pulled over just north of Alweber Road. A motorist following him called police to report that a 120-gallon propane tank had fallen off the trailer Prokey was hauling behind his van.

What police found when they pulled him over was 13 of the tanks welded together on the trailer. Prokey’s van, hand-painted black and with darkened windows, contained another tank.

“What’s that van look like to you?” asked Windham Deputy Fire Chef David Nichols to the media assembled a few hundred yards from the scene. “We’re ready for bad things to happen.”

“When we pull into something like this, the first thing that comes to mind is WMD (weapons of mass destruction) – post-9/11,” Nichols said. “We have to think of the worst and have all our safeguards and precautions in place.”

Officials said later that Prokey was cooperative, but they could not take chances with the potentially explosive tanks.

Firefighters from Windham and Gorham and members of the Presumpscot Valley Hazardous Materials response Team set up nearby and members of the state police commercial vehicle enforcement unit joined Windham police to investigate.

Daniel Tucker said his friend, Prokey, was planning to use the tanks as part of a boat he’d been building for four years off and on.

“This was parked in front of my house last night,” Tucker said, referring to trailer loaded with tanks. Tucker said he heard about the incident, he went to check on his friend, though he was unable to see him.

Tucker said Prokey previously had run the watercraft down a stretch of the Saco River last year, from Lovell Pond to Hiram Bridge, he said.

Prokey had since added walls and a roof to what had been a large raft supported by 55-gallon drums, Tucker said. The extra weight needed additional buoyancy, he said

Prokey may be handy, and creative in a way some Mainers would admire, but he’s not good about following the rules, said Trooper Charles Granger, with the commercial vehicle enforcement unit.

“You name it, he violated it – just about every hazardous materials violation we have,” Granger said of Prokey’s trailer load of fuel tanks. “It’s not safe at all. That’s why we have regulations and why we have companies haul hazardous materials, not (private) people.”

Granger said Prokey did not have the required licenses, nor display the required placards identifying the materials he was hauling, among other violations.

“We could have had a catastrophic incident over here,” Granger said.

Most of the tanks had some propane remaining in them, said Deputy Windham Fire Chief John Wescott; and while there was an odor of propane, there were no unsafe readings on firefighters’ meters.

Just in case, the Cumberland County Emergency Management Agency developed a response plan that included a model of where fumes would spread if the propane tanks started to leak.

Emergency personnel at the scene asked area residents to stay in their homes until the situation was declared safe, Nichols said.

Shortly before 3 p.m., workers with Shaw Brothers used a boom truck to hoist the trailer onto a flatbed which was then driven to a Gorham gravel pit. Wescott said the remaining propane would be burned off under the direction of the safety team for Downeast Energy, the natural gas utility.

Prokey was charged with theft by receiving stolen property for possessing a stolen propane tank worth $400, said Windham Lt. David DeGruchy. He was released on bail later in the day.

River Road was closed for more than four hours and motorists were detoured around the area where the van and trailer were pulled over.

Correction: This story was revised at 1:12 p.m., April 4, 2012, to correctly name the company whose safety team supervised the burning off of remaining propane. it was Downeast Energy, the natural gas utility.