Some clients of Nomura Holdings are restarting business with the brokerage after it took steps to address concerns arising from a regulatory probe into market manipulation, according to people with knowledge of the matter.

The country’s megabanks have resumed trading activities with Japan’s biggest securities firm, the people said, asking not to be named because the information is confidential. At least four insurers that had halted their equity or bond dealings with Nomura are also restarting these activities, they said.

Many of the firms returned to Nomura after the brokerage explained to them measures it is taking to prevent a recurrence of the breach, the people said.