Leeds Rhinos are investigating allegations that prop Ryan Bailey posted jokes on Facebook about the Japanese earthquake and tsunami.
A club spokesman said: "We are taking the allegations very seriously."
The alleged comments from the 27-year-old have since been removed from the social networking website.
A 9.0-magnitude earthquake, the fifth-largest in the world since 1990, struck the north-east coast of Japan on Friday, triggering a massive tsunami.
At least 10,000 people are thought to be dead following the catastrophe, while there are fears of a nuclear disaster at the Fukushima Daiichi power plant, 220km (140 miles) from Tokyo.
Bailey, who has been capped four times by Great Britain and four times by England, has made 223 appearances for the Rhinos since making his debut in 2002.