U.S. Shipping Partners L.P. (NYSE:USS) shares are dipping 13% after Moody’s lowered its debt rating on the petroleum and chemical shipper. Along with other debt ratings, Moody’s cut USS Shipping Partners’ corporate family and probability of default ratings to Caa3 from Caa1. USS shares are already down about 45% since Monday after the Edison, N.J.-based firm reported that it swung to a first-quarter loss.

In Wednesday morning trading, USS shares are falling 13.66%, or $1.12, at $7.08. For detailed price information and recent news stories about U.S. Shipping Partners, click USS.