Two firefighters currently facing a $4 million lawsuit from their union are now facing fraud charges from Halton police.

Police announced the charges Tuesday, saying in a news release that the charges are in relation to funds donated to the head office of the OPFFA (Ontario Professional Firefighters Association) in Burlington on behalf of families of firefighters injured or killed in the line of duty.

Colin Stuart Grieve, 58, of Stoney Creek, and Warren Paul Atkinson, 52, of Newmarket, were arrested today on charges of fraud over $5,000, money laundering, and attempting to obstruct justice.

We're obviously encouraged by the news today, given that the authorities are taking the appropriate steps to bring these two individuals to court. - Rob Hyndman, OPFFA president

"My client's position is obviously that they dispute these charges," said lawyer Gavin Tighe, who is representing Grieve and Atkinson in the civil case.

According to police, Between May 12 of 2011 and Feb. 26, of 2014, the two men had conducted advocacy work to help families of retired and dead firefighters from all over Ontario to apply for Workplace Safety and Insurance Board (WSIB) benefits.

"The [Ontario Provincial Fire Fighters Association] received a complaint, which caused them to conduct an internal investigation into donations," a police press release reads.

"The investigation revealed several large donations to the OPFFA that were never received, all linked to Atkinson and Grieve."

Det. Sgt. Chris Lawson of Halton's police's regional fraud unit told CBC News the two men were working on behalf of families to get WSIB settlements. According to a Toronto Star story from last year, the union says the men helped recover more than $100 million for their clients.

Lawson said the allegation is that after helping to settle with WSIB, the two men would then ask the family if they would like to donate to the union. However, they would then allegedly divert some of those funds for themselves, he said.

Police say the diverted funds were worth about $250,000.

OPFFA president Rob Hyndman told CBC News that the criminal charges are "somewhat of a validation" for the union.

"We're obviously encouraged by the news today, given that the authorities are taking the appropriate steps to bring these two individuals to court," he said.

"They were saying they were doing this on our behalf."

Last year, the union filed a lawsuit that accused the two men of bilking parts of settlements from widows and families of firefighter retirees.

Hyndman confirmed that lawsuit is still before the courts.