Four baboons escaped from the Texas Biomedical Research Institute last week - but were recaptured within 30 minutes.
The animals escaped by rolling a 55-gallon barrel to the edge of their enclosure, then standing it upright and using it to scale the fence.
Around 2,500 animals - including 1,100 baboons - are kept at the facility. According to the lab in San Antonio, the animals 'aid our scientists in the search for new diagnostics, drug therapies and vaccines'
The lab added that the baboons were not used in any infectious disease research and the animal capture team wore protective equipment for the safety of the animals.
The barrel the animals used to plan their escape was provided as an 'enrichment' toy in what critics have described as a 'barren and dusty' outdoor pen.
According to the lab, it has now removed the barrels and suggested that they will be replaced with smaller versions.
One woman captured the escape on camera
'Intelligent and sensitive'
Monica Engebretson is the North American Campaign Manager for global organization Cruelty Free International.
She said: "Under the U.S Animal Welfare Act laboratories are required to provide primates with 'enrichment' to help alleviate boredom for these highly intelligent and sensitive animals.
"Unfortunately, many laboratories provide the bare minimum required under the law and sadly this seems to be the case for the more than 1,000 baboons held at Texas Biomedical Research Institute."
'Does not translate'
According to Cruelty Free International: "Despite some superficial genetic similarity with humans monkey data does not translate well to human trials.
"We believe that there is a strong scientific case against using primates in research. Thanks to recent advances in technology there is a wide range of more human-relevant approaches to studying, understanding and contributing to the cure of many diseases.
"We are calling on the Institute to release these baboons from their bleak enclosures to live out their lives at reputable sanctuaries."