Riot police reacted when rice producers shut down four lanes of the Pan-American Highway near Divisa on Monday.
The rice producers are calling for an end to rice imports and exclusion from price controls.
Last December, the government committed to purchasing 500,000 quintals for $18 million from local producers. Ruben Zeballos, president of the Rice Importers Association of Veraguas said that Panama imported 8,700 quintals of husked rice from Argentina during the first week of January, La Prensa reports. Agricultural authorities deny the claim.
Police, reportedly numbering in the hundreds, used gas spray to disperse the demonstrators and arrested four who were later released. At least one officer was injured.
Producers are scheduled to meet with President Juan Carlos Varela next week.