A deadly explosion at Iran’s largest port is believed to have been caused by missile fuel ingredients sent by China.

At least 40 people were killed and more than 1,000 were injured in the blast in Shahid Rajaei port on Saturday, which the state-run Islamic Republic News Agency said was likely triggered by containers of chemicals.

The agency did not specify which chemicals they were but it was reported in January that China was to ship sodium perchlorate, a common missile fuel component, to Iran after its supplies ran low following attacks on Israel.