NEWPORT BEACH — Arborists saw no signs of disease in a city-maintained tree before it fell and killed a motorist in September, the city's top administrator said Tuesday.

The statement comes as newly released records show that many of the other city-maintained blue gum eucalyptus trees are infected by sulfur fungus, which causes root rot and the eventual collapse of trees.

"On the tree that fell, there were no external signs of disease — no fungus, no conks, no fruiting bodies, no lifting of the roots, no visible signs of trouble in the leaves, roots or on the trunk," City Manager Dave Kiff wrote in an email.

The written statement was the first time Kiff has publicly stated that the tree showed no outward signs of disease before it fell. Newport's arborists do not typically inspect eucalyptus trees' roots below ground, Kiff claims, because doing so would expose the roots to fungus.

Newport's trees are regularly inspected by both city-employed arborists and the city's tree-maintenance contractor, West Coast Arborists.

While the tree in question on Irvine Avenue straddled the city's border with Costa Mesa, it was maintained by Newport Beach.

Last week, the city released records indicating that West Coast Arborists knew some eucalyptus trees on Irvine Avenue were infested by bugs and showed signs of decay, although the notes did not specifically flag the doomed tree.

After that tree fell and killed Tustin resident Haeyoon Miller on Sept. 15, the city hired certified arborist Dan Jensen to analyze all blue gum eucalyptus trees in the city's care.

Three of those reports were released Tuesday morning, but they do not cover the Irvine Avenue trees.

Jensen found that some trees throughout the city are clearly infected by sulfur fungus, and some could fall on peoples' homes, on bike paths and on streets, according to the documents.

Many trees have conks, or "fruiting bodies" growing from them, which is "the sure sign of the disease," Jensen wrote in one of his reports.

Jensen emphasized that trees could look normal from above ground, yet have "a severe case of root rot."

Officials could not say Tuesday how long they have known that many of city's eucalyptus trees were diseased. Jensen wrote that Newport's blue gums have a "history of root fungal activity."

Today, more than 50 blue gum eucalyptus trees are at such a high risk of falling that they should be quickly removed, the reports say. Some of them threaten peoples' bedrooms. Already, officials have directed the emergency removal of about 140 trees since September.

"As there is no fool-proof test for root rot, an aggressive approach may be taken to protect the public," Jensen wrote.

He analyzed eucalyptus trees throughout the city, but officials have refused to release the tree reports from Irvine Avenue.

City Attorney Aaron Harp said the Irvine Avenue reports were initiated by his office, and are exempt from the California Public Records Act. The city released other reports Tuesday in response to public-records requests made by the Daily Pilot and other local news organizations.

Those reports cover trees in Corona del Mar, on the Balboa Peninsula, near Lido Isle and the neighborhoods around Irvine Avenue.

Jensen recommended removing trees with fungal conks and others that leaned unnaturally, or one that threaten homes and people. Trees that ranked nine or higher on his 12-point scale should be "removed as soon as possible to protect the public," he wrote.

They show that the following trees are still recommended for removal:

•Twenty-four along the Groves Bike Trail, near Westcliff and Dover drives;

fourteen on Holiday Road;

four on Mariners Drive;

four trees on Pacific View Drive;

three trees on Via Lido;

two on 23rd Street; and

one on Santa Ana Avenue.

mike.reicher@latimes.com

Twitter: @mreicher