Germanwings co-pilot Andreas Lubitz, who crashed Flight 9525 into the Alps, may have spiked the pilot’s drink with a diuretic in order to get him out of the cockpit, a new report claimed Thursday.

The UK Daily Telegraph, citing German newspaper Express.de, reports that 27-year-old Lubitz may have mixed a drug into Captain Patrick Sondheimer’s drink, causing him to need to use the restroom and consequently leaving Lubitz alone in the cockpit.

Other reports suggest that Lubitz searched online for information about diuretics in the days leading up to the crash. However, the Telegraph notes that the reports appear to be based on speculation, with no evidence that Lubitz bought the drugs in question or took them onboard the doomed flight.

Investigators believe that Sondheimer was locked out of the cockpit by Lubitz after the captain left to go to the bathroom. Sondheimer is heard on the cockpit voice recorder banging on the door and demanding to be let in moments before the plane crashed into a mountainside, killing all 150 on board the March 24 flight from Barcelona to Dusseldorf.

Click for more from The UK Daily Telegraph.