BURLINGTON, Ont. -- Police say it appears five robbers lived for days in an abandoned second-storey office, using heavy tools to break through the floor into a bank in southern Ontario, in a heist investigators call "unrivalled" in its sophistication.

Five men face charges in connection with a Hollywood-style robbery that involved breaking through thick concrete walls and using high-tech equipment to bypass intricate security systems at a bank in Burlington, Ont.

While police are still calculating how much was seized, they allege the men were trying to make off with at least $300,000 in cash and several thousand more in jewelry.

"Based on the level of sophistication and planning involved, the individuals involved are clearly not amateurs," said Deputy Chief Andrew Fletcher of Halton regional police.

Officers were dispatched to a Toronto Dominion/Canada Trust financial institution around 1 a.m. Monday after an alarm went off.

They arrived to find the bank's exterior doors secure but after searching the area with the help of a canine team, five men were found hiding in a nearby field.

"The suspects were found to be in possession of walkie-talkie radios and two large hockey-style duffel bags containing a large amount of money, jewelry that was later determined to have been stolen from the bank vault and from within the bank's security deposit boxes," Fletcher said.

But what police find most remarkable is just how the alleged robbers got their hands on the loot.

They say it appears the suspects broke into an abandoned second-storey office space above the bank, where they stayed for several days.

During that time, police say heavy-duty tools were used to break through the concrete floor of the office into the ceiling of the bank.

When it came to getting into the bank's vault, more stealth tactics were used, police said.

"The suspects used sophisticated electrical equipment to bypass the bank's alarm system and then forced entry through a two-foot thick reinforced concrete ceiling into the vault of the bank, where they began removing money and valuables that were found therein," Fletcher said.

After finding the five men, police say they also found three vehicles which were carrying equipment believed to have been used in the break-in.

Those tools included an acetylene oxygen tank, concrete cutting saws, rappelling equipment, ladders and lighting equipment.

"There's no question that a great deal of effort and planning went into this offence," said Fletcher.

John Hickey, 44, of Caledon, Ont., Aldo Simoni, 31, of Toronto, and Alexander Papic, 48, Mentor Vishjay, 36, and Besim Rugova, 32, all of no fixed address, are all facing charges of break, enter and commit, and possession of break-in instruments.

The men appeared in a Milton, Ont., court on Monday and have been remanded into custody until Thursday, when they're set to have a bail hearing.

Investigators are now trying to determine if the accused could be suspects in other incidents. Halton police say more charges could be forthcoming.

A TD bank spokesman said the bank has been working to contact all customers affected by the attempted robbery and emphasized Wednesday that its facilities remained secure.

"While we don't share specific details on our security systems for obvious reasons, what I can tell you is we have robust security procedures with backstops and multiple layers. As a result, these suspects were caught," said Mohammed Nakhooda.