You can technically accept multiple offers, as long as they are offers without deposit. Remember – your property is not officially secured until the tenant pays a holding deposit. During this time, your listing will still stay on the market, and you can receive and accept other offers.
If you accept multiple offers, the property will go to the tenant who pays the holding deposit first. It basically becomes a race between the two on who pays first. You may want to give tenants a head-up if this happens.
Note: You cannot accept multiple offers with deposit. Offers with deposit have the deposit ready upon acceptance. Your property gets taken off the market and tenants move to referencing immediately. As a result, there isn't time for another renter to steal the property.