Mayor Colette Roy-Laroche announced this week that Montreal, Maine & Atlantic Railway has been told to immediately repay $4 million the community says it spent to cover the massive environmental mop-up.
The mayor's spokeswoman, Karine Dube, says the lawyer's letter calls upon the American railway to reply to the request before Thursday's noon deadline.
MMA president Robert Grindrod was unavailable for comment Wednesday and company chairman Edward Burkhardt did not immediately respond to messages left at his office.
An unattended MMA train pulling 72 oil-filled tankers derailed in Lac-Megantic's downtown core on July 6 — a crash that set off huge explosions and killed an estimated 47 people.
Roy-Laroche alleges MMA failed to pay crews it hired to clean up some of the millions of litres of crude oil that seeped into the environment from damaged rail tankers.
She alleges the municipality was forced to cover the railway's tab after some workers threatened to leave town.
The office of Maine Gov. Paul LePage also announced Wednesday that he would attend a memorial mass for victims in Lac-Megantic on Saturday.