A brief statement carried by Xinhua, citing the party's organisation department which is responsible for personnel decisions, said Yang had been stripped of his position as chief of the State Administration of Work Safety.
He is suspected of "serious breaches of discipline and the law", the report said, using the usual euphemism for corruption.
It gave no other details and it was not possible to reach Yang for comment. Officials are almost always fired soon after announcements of party graft investigations.
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The government has not explicitly linked Yang's case to the Tianjin incident, but the company that operated the chemical warehouse that blew up did not have a licence to work with such dangerous materials for more than a year.
Yang was vice mayor of Tianjin, a city of 15 million people, until 2012.
China has struggled in recent years with incidents ranging from mining disasters to factory fires which have caused deep public anger, and President Xi Jinping has vowed that authorities should learn the lessons paid for with blood.
Read MoreProtesters demand compensation for Tianjin blasts amid chemicalclean-up
The Tianjin disaster has again raised questions about safety standards following three decades of fast economic growth. A blast at an auto parts factory killed 75 people a year ago.
The government has confirmed there were about 700 tons of deadly sodium cyanide in the warehouse that blew up. The blasts devastated a large industrial site and nearby residential areas.
Xinhua said that 11 of the 12 apartment blocks worst affected by the explosions had been officially classified as structurally safe.
On Tuesday, Xinhua said that five Chinese state-owned property developers will buy apartments hit by blasts.