MOSCOW — An administrator for a Russian travelling circus says two rare Siberian tigers were among a group of big cats that died during a 20-hour truck journey this week.

Circus officials and police initially said that eight Bengal tigers had died.

But Mechta circus administrator Yevgeny Kudashkin said Thursday there were seven tigers. He says two of them were endangered Siberian tigers -- also known as Ussuri, Amur or Manchurian tigers.

A lioness also died during the trip across Siberia.

Veterinarians say they suspect the animals were suffocated by exhaust fumes in the enclosed and heated truck, but laboratory tests were not yet complete.

The animals were dead when they arrived Tuesday in the city of Yakutsk, where they had been due to perform.