Two Quebec women arrested in connection with a Mexico City firebombing have been ordered to remain in a Mexican jail for up to 40 more days.

A spokesman for Mexico's federal attorney-general says a judge has ruled that Fallon Rouiller-Poisson and Amélie Pelletier will stay behind bars while local authorities continue their criminal investigation into the attack.

Rouiller-Poisson and Pelletier were apprehended in the capital earlier this week after Molotov cocktails damaged a building that houses a federal government office and a nearby car dealership.

The attorney-general's office says that for now the case is being considered vandalism — but adds that the ongoing investigation could lead to more serious criminal charges.

Rouiller-Poisson, a 20-year-old from Montreal, and Pelletier have yet to be charged with any crimes.

The office says the women could be released before the 40-day period expires if they produce evidence that proves their innocence.