A brazen attempted heist at London’s Dulwich Picture Gallery was foiled by security on Wednesday night—but the suspect has so far managed to evade capture.

Shortly before midnight, a burglar entered the museum, targeting a pair of works by the Dutch master Rembrandt van Rijn on view in the exhibition “Rembrandt’s Light.” While the intruder did manage to remove the works from the wall, he wasn’t able to successfully spirit them away from the premises.

Police encountered signs of forced entry and quickly located the suspect mid-heist. He sprayed an officer with an unknown substance, according to a statement, and managed to escape without arrest. The officer was not injured.

“This was an audacious attempted burglary and was clearly planned in advance,” Detective Inspector Jason Barber from the Flying Squad, a branch of the London police, said in a statement. “Two paintings in the exhibition were targeted and it was only down to the prompt response of gallery security staff and the courage and swift intervention of officers that these two works of art were not stolen. Thankfully both the paintings were quickly recovered and secured.”

Dulwich Picture Gallery. Photo Stuart Leech.

The gallery said the intrusion was identified in part thanks to a new “state-of-the-art” alarm system they installed specifically for this high-profile show. The museum is now working to assess whether the works suffered any damage during the attempted heist.

The museum declined to confirm which works in particular the thief was after, but said that they remain safe and sound. “The intruders were detected by the gallery’s robust security systems and, thanks to the immediate intervention of security staff and the swift response of the Metropolitan Police, the paintings were secured at the scene,” a representative said in a statement.

The show—one of a wave of exhibitions organized to mark the 350th anniversary of the painter’s death around the globe—includes high-profile loans from the Louvre in Paris and the Rijksmuseum in Amsterdam.

The exhibition and the gallery at large will remain closed until further notice to allow police to conduct a full investigation.