SENATORS on Tuesday urged the government to investigate the inoculation of 100,000 Chinese workers at offshore gaming companies in the Philippines using a smuggled coronavirus vaccine from China.

Authorities should prosecute those behind the smuggling, distribution and sale of unauthorized vaccines in the country, they said.

“The government should act immediately to identify and prosecute the source of these smuggled, unverified and therefore dangerous vaccines, which threaten the effectivity of our health response to COVID-19,” Senator Risa N. Hontiveros-Baraquel said in a statement.

She said the Health department, Food and Drug Administration (FDA) and Health Technology Assessment Council should be stricter in enforcing the vaccine approval process and ensure that violators are held liable.

This comes before a Senate committee of the whole hearing on the COVID-19 immunization plan, set for Jan. 11, which Senator Franklin M. Drilon said should also cover the inoculation of the Chinese workers.

“The Senate should continue with the hearing, especially in the light of the revelation that 100,000 POGO workers were inoculated in the country. That is illegal,” he said in a statement.

“In aid of legislation, the Senate must get information from other sources on how to strengthen the FDA and the Bureau of Customs to prevent similar episodes in the future,” he added.

This followed the vaccination of presidential security guards (PSG) using an unregistered vaccine, which the House of Representatives also wants to probe.

President Rodrigo R. Duterte on Monday night urged lawmakers to stay away from the issue, adding that soldiers were not obliged to testify at the hearings.

“Do not threaten them with prosecution and things like that,” he said. “They have every right to live and to invoke self-preservation.”

Mr. Drilon said it is within Mr. Duterte’s executive privilege to prevent his guards from attending the hearings, but the chamber could still tap other sources to get the information.

“There is no preventing Congress from eliciting information in aid of legislation from other resource persons,” he said.

Senator Richard J. Gordon said Mr. Duterte should “respect” the separation of powers between the Executive and Legislative branches.

“I stand by the independence of Congress,” he told an online news briefing. “No one can overwhelm the other and put it into submission, in the same way that we can’t bully the Executive and threaten them with investigations.”

A bloc of congressmen filed a resolution seeking to investigate the smuggling of the vaccines from China for the presidential guards.

The opposition lawmakers said the Presidential Security Group (PSG) had violated several laws and their oath of office when they agreed to be inoculated with the smuggled drugs. The PSG could have also violated the law against corruption.

The National Bureau of Investigation (NBI) said it would continue its probe of the smuggled vaccines.

“The NBI investigation will proceed as planned,” Justice Secretary Menardo I. Guevarra told reporters in a Viber message.

“Its mission is to investigate the alleged proliferation of unregistered anti-COVID-19 vaccines and their unauthorized administration in the so-called black market,” he added.

Mr. Guevarra said the agency has several sources of information other than the PSG.

NBI Deputy Director and spokesman Ferdinand M. Lavin separately told CNN Philippines they have asked the FDA if it had approved some vaccines for local use. They also expect to reach out to the Bureau of Customs on the smuggling.

The NBI will also reach out to PSG commander Brigadier General Jesus Durante III through the Armed Forces. “If he declines to cooperate, the investigation will continue and we will build up the case on independent evidence,” he said in mixed English and Filipino.

Mr. Lavin said they would talk to civic leader Teresita Ang-See, who divulged the vaccination of the Chinese POGO workers. — Charmaine A. Tadalan, Vann Marlo M. Villegas, Kyle Aristophere T. Atienza and Gillian M. Cortez