The Therapeutic Drugs Administration (TGA) has issued another recall of Valium.

Drug manufacturer Arrow Pharma is recalling all batches of Valpam 5 tablets supplied in blister packs of 50, after some were found to have been swapped with different drugs.

Manufacturer Roche was recently forced to recall all packs of 50 Valium 5 milligram tablets after different drugs were found in packets.

“We suspected a couple of weeks ago that these diazepam tablets — or Valium is the trade name for some of them — are being diverted and sold on the black market,” deputy secretary at the Commonwealth Health Department, John Skerrit said.

“They can be abused.

“[This time] it's the same product but it's a different supplier of the product, so it's a different case.”

The two cases come from different manufacturers, but police are investigating distribution centres.

“There is a police investigation underway and we expect linkages but we don't know if it is the same perpetrator or a copycat,” Mr Skerrit said.

The drugs were being replaced with other drugs such as Sandoz Amlodipine 5mg and paracetamol codeine tablets.

Diazepam tablets sell for between $10 and $30 on the black market.

The TGA is asking pharmacists nationwide to check all packages of Valium they dispense, and for any patients who suspect their pack may have been tampered with to return them to their pharmacy.

The regulator says the distribution centres involved are taking measure to increase scrutiny and security.