The FDA has updated its list of blood pressure medications that are being recalled after traces of a cancer-causing ingredient were found in several batches.

The agency last month said it was recalling valsartan tablets made in China after tests showed some contained Nitrosodimethylamine, or NDMA, a probable carcinogen.

On Aug. 8, the recall was expanded to include tablets from AvKare, A-S Medication Solutions LLC, Bryant Ranch Prepack Inc, Camber Pharmaceuticals, Inc. H J Harkins Company, Northwind Pharmaceuticals, NuCare Pharmaceuticals Inc., Prinston Pharmaceutical Inc. (labeled as Solco Healthcare LLC), Proficient Rx LP, Remedy Repack, Teva Pharmaceuticals (labeled as Major Pharmaceuticals), Teva Pharmaceuticals USA (labeled as Actavis).

Some lots of valsartan distributed by Teva Pharmaceuticals were part of the original recall. The new list adds more lots.

The new recall list includes drugs manufactured from valsartan by Hetero Labs Limited in India labeled as Camber Pharmaceuticals Inc. But not all Camber products are being recalled, the FDA said.

Originally, the recalled drugs were manufactured by Zhejiang Huahai Pharmaceuticals, Linhai, China. The factory in India uses a similar manufacturing process to the one in China, and the FDA believes the impurity resulted from a change in how the drug is made. The U.S. Food and Drug Administration says its investigation into how the impurity got into the valsartan tablets is continuing and more brands could be added to the recall list

It is also updating its list of brands not included in the recall.

Patients who have been prescribed these drugs are advised to talk with their doctor or pharmacist about switching to a different company's product. They should not quit the drugs until they are given a replacement, the FDA said.

Patients who have a negative reaction to a valsartan-containing drug can report it to the FDA's MedWatch program by downloading a form online.