CAPE CANAVERAL, Fla. — Space Exploration Technologies is delaying its next supply run to the international space station after discovering an oily residue on thermal blankets that protect the trunk of the Dragon cargo capsule, according to a source. Engineers were concerned the substance could outgas once the capsule was in orbit and potentially contaminate experiments in the unpressurized trunk, which also houses Dragon’s solar panels.

SpaceX spokeswoman Emily Shanklin did not respond to a request for comment. The Hawthorne, Calif., company announced the delay afternoon of March 13 in a brief statement saying it needs “additional time to resolve remaining open items.”

Launch of SpaceX’s ninth Falcon 9 rocket had been slated for 4:41 a.m. EDT from Cape Canaveral Air Force Station in Florida. Liftoff is now targeted for March 30, with April 2 as a backup date.

The flight will be the third of 12 cargo runs to the station under the firm’s $1.6 billion contract with NASA.