Insider trading by WA government staff following a major contract decision can't be ruled out, the transport minister says, but insists his office wasn't privy to the information before a share price surge.

The Australian Securities Exchange queried NRW Holdings in February before and after it announced it had won the design, construction and maintenance contract for the $2 billion Forrestfield Airport Link, noting its share price had soared. The contract award was announced on February 18 but the company’s share price moved…