Indian news networks said that a letter addressed to the Israeli ambassador was found close to the scene of the explosion. The Indian Express reported that the letter was typed and “abusive.” No further details were given.

The report said investigators were working to establish if there was a connection between the letter and the explosion.

The Foreign Ministry said Israeli security officials were working with local Indian authorities on the investigation.

In an interview with Indian television, embassy spokesman Guy Nir said staff heard the explosion from within the building.

“Around 5:08 [p.m.], we heard a blast. We believed it to be close and later we found out it was in close proximity to the embassy,” Nir said. “We have the Delhi police and our security team over there investigating the situation.”

Deputy Ambassador to India Ohad Nakash Kaynar told Asian News International that Israeli security teams “are working in full cooperation with local Delhi security and they will investigate the matter further.”