KANDAHAR, Afghanistan — National Defence is looking to buy more specialized armoured vehicles to detect roadside bombs, the biggest scourge facing troops in Afghanistan, The Canadian Press has learned.

The army is drawing up a proposal to purchase as many as 30 vehicles for both overseas and training duty, say senior Defence sources in Ottawa.

"Commander CEFCOM (Canadian Expeditionary Force) is asking for greater capacity,'' said a source who has seen the planning. "We're interested in buying larger numbers so we have more deployable sets.''

The Expedient Route Opening Capability system -- known by its acronym EROC -- involves three vehicles working in tandem to sweep roadways before the arrival of combat or supply convoys.

The Defence sources, who spoke on the condition of not being named, said last week that the proposal involves buying 10 more EROC sets sometime in the near future.

The Canadian army already has five sets -- or 15 trucks in total -- that were purchased from the U.S. Marine Corps last spring. It will not say how many of them are deployed in Afghanistan.

The plan for additional mine clearance vehicles is being drawn up by the army's land staff division, but has yet to be approved by the Conservative government.

"We haven't gone to government to ask permission yet, but it's one of those things we're going to have to do,'' the source said.

The purchase is expected to run in the range of $60-million.

Parliament's extension of the mission in southern Afghanistan has sent military planners into an inventory frenzy. They're trying to determine what equipment needs replacing, upgrading, or augmentation in order to carry on the mission until 2011.

The vast majority of the 82 Canadian soldiers killed in Afghanistan have died in roadside bombings -- or improvised explosive device (IED) attacks.

Field engineers, who operate the EROC vehicles, gave the proposal an enthusiastic thumbs-up.

"The IED threat in Kandahar is great,'' said Capt. Rob Horton, 35, operations officer of 12 Field Squadron, based in Edmonton. "And if we are going to put a vehicle on the road and the vehicle affords our operators blast protection from Point A to Point B and potentially (explode) an IED and not get seriously injured, that is something we are interested in.''

Horton, who sees reports from all road crews, says they've found and disposed of a number of roadside bombs using the system, but for security reasons wouldn't say how many.

Sgt. Tim McCormick, 37, recently led a team of eight engineers down a particularly dodgy stretch of road when their Buffalo -- one of three in the EROC chain -- struck a powerful roadside bomb.

A few months ago, he had survived a previous, smaller blast in a LAV III armoured vehicle, which combat engineers drove before the specialized trucks were purchased.

When McCormick recently hit the second bigger bomb, the first thought that went through his mind was: ''Grab the seat!''

Once everything settled down, he cursed, jumped out and went looking for other mines "as if nothing had happened.''

McCormick said he was skeptical of the vehicles at first, partly because they seem to take forever to get anywhere, but the bomb strike made him in an instant convert.

"They save lives, they increase the confidence level of the troops doing this stuff and it makes it easier to screw off the IEDs that've been planted for us to step on,'' said McCormick, 37, who is based in Edmonton.

He then added at the end of the interview: "They need to buy more vehicles and they should stop thinking about it.''

The first Canadian deaths attributed to IEDs happened outside of Kabul on Oct. 2, 2003 when a lightly protected Iltis jeep rolled over a mine, killing Sgt. Robert Short and Cpl. Robbie Beerenfenger.  Since then, the army has scrambled to provide more heavily armoured vehicles for soldiers and better detection capabilities.

The U.S., bloodied by five years of fighting in Iraq, leads the way in both technology and proven equipment.  When NATO took over operational command in southern Afghanistan, American mine-clearing trucks became less available, forcing Canada to purchase its own in the spring of last year.

The Defence sources in Ottawa acknowledge the vehicles in theatre have been beaten up, but are continuing to prove their worth every day.

"They've taken a pounding, but they're designed to go out and take a pounding and clear routes and not have the LAV targeted -- or so other less protected vehicles,'' the Defence source said.

In road clearance operations, three different vehicles -- the Husky, the Buffalo and the Cougar -- work as a team to uncover mines and booby traps buried in dirt roads or tunnelled in beside paved highways.

The Husky, which looks like a souped-up road grader, uses metal detectors to stop the often home-made weapons and can even X-ray the ground once it's detected something. After marking the location, the Buffalo moves into place with a digging arm to remove -- or detonate -- the threat, while the Cougar acts as a command vehicle.