Wall Street’s commitment to buying back auction rate securities grew to more than $65bn as five more firms agreed to repurchase such debt instruments from investors in settlements with regulators investigating the market’s collapse.

Brokerage firms SunTrust Investment Services, SunTrust Robinson Humphrey, Comerica Securities, First Southwest Company of Dallas, and WaMu Investments, have agreed in principle to buy back more than $1.8bn in ARS and pay a total of $3.25m in fines, according to the Financial Industry Regulatory Authority, a non-governmental regulator for securities firms doing business in the US.