HONOLULU -- The threat that the Hawaii Superferry will spread invasive species has brought up the issue of whether other interisland shippers pose the same threat. However, it turns out that interisland shippers Young Brothers and Matson have already been facing much tougher oversight.

At Young Brothers cars being shipped interisland get a 10- to 15-minute inspection. Unapproved plants are rejected, but this check is mostly to document the vehicles condition before shipment.

"We just do one quick check, ashtrays, everything intact; nothing's cracked, broken, missing. If not, we list them all," Young Brothers freight clerk Ramon Masaki said.

Hawaii Superferry officials said they are proud of their inspections for plants, animals and bugs that include popping trunks and engine hoods, which the state might soon require of Young Brothers as well.

"It's just that I think Superferry has just put the bar a little bit higher," said Carol Okada of the Department of Agriculture.

Young Brothers officials said they are not worried about one more step in car inspections. However, its container operations are already under higher scrutiny. State inspection teams that used to come three months apart now show up every few days.

Fear of species like the noisy coqui frog led to a doubling of the state's inspection budget.

"We need to protect the state much better and control the spread of what's already established," Okada said.

Young Brothers' bigger concern is that, due partly to the concerns raised about Superferry, the state might want to look inside more of the 500,000 containers it moves every year.

"I think once we get into opening individual containers, then we do have issues of cargo slow down, and our customers will have issues with our delivery times," said Roy Catalani of Young Brothers.

That could mean slightly higher costs for goods shipped interisland.