A Boeing 737 jet departing from Tehran, the capital of Iran, crashed after takeoff killing the 176 people on board early Wednesday (Jan. 8) morning.

The jet was headed to Kyiv, Ukraine and was operated by Ukrainian International Airlines. Onboard was 167 passengers and nine crew members. The cause of the crash is currently unknown but is being considered a mechanical error by Iran’s Fars news agency. A full report of the crash may take months. The plane crashed minutes after taking off from Tehran.

The Ukranian embassy in Iran state an engine failure was the cause of the crash but backtracked and said: “any statements regarding the causes of the accident prior to the decision of the commission are not official.”

CNBC details the Boeing 737-800 jet is an older model than the Boeing 737 Max that was shut down after two crashes in Mid-March 2019.

The crash occurred hours after Iran attacked U.S. military bases with ballistic missiles, causing some to wonder if a stray missile caused the crash.

Onboard the flight was citizens of Canada, Iran, Sweden, and Ukraine. The Foreign Minister of Ukraine said four passengers included Afghanistan, Germany, and Britain. Reuters reports the black box has been recovered but there are no details if it will be sent elsewhere to be analyzed. Flights into Tehran are currently suspended.