Two subway trains were bombed by graffiti -- completely covered in paint -- over the weekend, according to transit employees who found the cars in the MTA's Jamaica Yard on Monday morning.

"The truth is if graffiti artists have the time to do all this work, then there’s more than enough time to sabotage the system or equipment in other ways. This @MTA @NYCTSubway system isn’t safe," read a tweet from Progressive Action, a transit workers' advocacy group.

Some of the graffiti sported messages such as "Drugs All Day!" and "Don't Come Here!"

Another video posted online Sunday of a train covered in graffiti may be of the same incident:

“The facts are that major graffiti incidents systemwide were down in 2019 despite alarmist claims to the contrary," said MTA Chief Safety Officer Patrick Warren in a statement Monday. "We have zero tolerance for these incidents, which take passenger trains out of service and take away valuable resources and thousands of dollars from critical system improvements. New York City Transit continues to work closely with the NYPD to hold those accountable for these incidents to the fullest extent of the law as the safety of our customers and employees is our top priority.”

The MTA said graffiti can take up to a week and cost several thousand dollars to remove from a train that's been covered. The time necessary to completely bomb a train means these happen while the trains are parked overnight between stations or in rail yards. Last year, the MTA said there were were 242 track layup hits and 36 yard hits, including these two incidents.

The NYPD oversees security on tracks and NYC Transit handles security in yards. The NYPD is using more sophisticated means of detection such as infrared glasses and has partnered with other police departments in America and abroad "on long-term investigations to identify and capture vandals responsible for major hits," according to a Wall Street Journal article Monday.

In 2018, when the MTA reported a recent high of 376 major hits, the NYPD arrested three Spanish nationals for allegedly vandalizing subway train cars with "European style graffiti" in the Bronx, Brooklyn, Manhattan, and Queens. One of the taggers insisted at the time he had no idea tagging was illegal: "In Spain, it is normal and not a serious crime."

It was not immediately clear what line the graffiti'd trains were set to run on, or whether they have been pulled from service for cleaning.