The Food and Drug Administration (FDA) has reportedly broadened its investigation into a serious illness suffered by a patient participating in AstraZeneca’s COVID-19 vaccine testing trials.

Reuters reported Thursday that FDA officials will seek data from Oxford University, AstraZeneca’s testing partner, regarding trials of vaccines for other diseases unrelated to COVID-19 in the hopes of determining whether patients in those trials developed similar side effects.

The move comes after the AstraZeneca-Oxford project was put on hold in early September due to one British trial participant falling ill with what was believed to be the rare spinal condition transverse myelitis.

“It just shows that the FDA is being thorough,” one source familiar with the probe said to Reuters.

The widened scope of the probe reportedly does not indicate a view by the FDA that AstraZeneca’s trials are unsafe or that other vaccines used in trials by Oxford were unsafe either, according to the sources, who noted that some delays have occurred due to Oxford’s data being presented in a different format from what the FDA has requested.

The FDA declined to comment to Reuters, while AstraZeneca pledged to continue working with the agency to deliver a COVID-19 vaccine.

“We are continuing to work with the FDA to facilitate review of the information needed to make a decision regarding resumption of the U.S. trial,” said a company spokesperson.

A number of private companies are pursuing COVID-19 vaccines in various stages of clinical trials, including drugmakers Pfizer and Moderna; AstraZeneca is also conducting clinical trials in other countries besides the U.S., including the U.K. and India.