OTC Markets Group is increasing the number of network providers that support its trading system after an outage knocked out trading for more than five hours on November 7, the company's chief executive said.

The loss of connectivity, which was aggravated by tight security at OTC's New Jersey data centre, froze trading in thousands of unlisted shares, including those of heavily-traded Fannie Mae and Freddie Mac. The failure also highlighted concerns about problems in the electronic infrastructure underpinning US exchanges.