(Recasts with flight resumption)
BEIJING May 22 (Reuters) - Two Chinese flights bound for the troubled far western region of Xinjiang resumed after being diverted to other airports when a passenger said his travelling companion had threatened to blow up one of the aircraft, state media reported on Thursday.
All passengers were searched and nothing was found, the official Xinhua news agency quoted police as saying.
Both planes were operated by Juneyao airlines and flying from the commercial capital, Shanghai, to the city of Urumqi, where, hours earlier, blasts at a street market killed 31 people and injured 94. Authorities labelled the attack an act of terrorism.
Juneyao said a passenger on the first flight had passed the crew a note saying his travelling companion had threatened in a telephone call to blow up the plane. His companion had failed to board the flight and he was suspicious of the contents of a piece of luggage entrusted to him.
The plane was then diverted to the northwestern city of Lanzhou.
The airline said the travelling companion then boarded a second flight to Urumqi, which was diverted to Nanjing.
The official China News Service, quoting Nanjing airport police, said a suspect was arrested "in a common criminal case". It did not say whether the arrest was connected to the alleged threat to blow up the first plane.
Separately, state media said police sealed off a train station in Lanzhou after detecting what reports initially described as suspected explosives.
But authorities later said no explosives were involved, the Xinhua reported on one of its microblogs. The station later resumed normal activity, Xinhua said. (Reporting By Megha Rajagopalan, Li Hui, Sui-Lee Wee and Paul Carsten; Editing by Nick Macfie and Ron Popeski)