SandRidge Energy Inc. and Breitburn Energy Partners LP (NASDAQ: BBEP) filed for bankruptcy protection on May 16, the latest U.S. oil and gas companies to fall victim to weak oil prices.

A plunge in global crude prices has now pushed at least 28 publicly traded North American oil and gas producers to seek bankruptcy protection since early 2015, according to a Reuters review of regulatory filings.

SandRidge said in a court filing that it had total assets of $7.01 billion and total debt of $4 billion as of March 31.

Breitburn listed assets and liabilities of $1 billion to $10 billion.

SandRidge, which has been in talks with creditors on a restructuring deal, said on May 11 it would not be able to file financial results for the quarter ended March 31 on time.

Small oil and gas producers have largely exhausted funding alternatives after issuing more equity and debt, tapping second-lien loans and shedding assets over the last two years to stay afloat as banks trim credit lines.

The SandRidge case is in U.S. Bankruptcy Court, District of Southern Texas, Case No: 16-32488.

The Breitburn case is in U.S. Bankruptcy Court, Southern district of New York, case no: 16-11385-smb.