A Russian researcher at Harvard University is being detained over failing to declare frog embryos while passing through customs, according to a filing by her attorney.

Kseniia Petrova's attorney said her previous arrest in Russia and social media activity "will almost certainly ensure a nice, hefty jail sentence for her" if she is deported back.

A Russian scientist at Harvard Medical School was detained by ICE in February after she failed to declare frog embryos at customs.