A 40m-tall heritage tree that toppled and killed a woman at the Singapore Botanic Gardens in February did not have a cavity in its trunk that was a result of decay, said a senior National Parks Board (NParks) official, countering an earlier assessment by an independent arborist.

Rather, the hollow, which measured 1.5m long, 0.2m deep, 1m high and 0.3m wide, was a flute, said Mr Elango Velautham, deputy director of the Botanic Gardens' Aboriculture and Plant Resource, who inspected the tree after the report was made on Sept 29 last year.

A flute is an irregular feature of a tree caused by uneven growth patterns that may appear to be concaved inwards, or extruded outwards, as opposed to a cavity, which, according to the International Society of Arboriculture, is an open or closed hollow within a tree stem, usually associated with decay.

"There was no decay, no cavity," said Mr Elango, testifying yesterday, on the second day of an inquest into the death of Indian national Radhika Angara, who was crushed when the tree fell on Feb 11.

The 38-year-old regional digital marketing head for Asia-Pacific at MasterCard was attending an outdoor concert at the Shaw Foundation Symphony Stage with her French husband, Mr Jerome Rouch-Sirech, 39, and their twins, aged one.

Her husband, children and a 26-year-old Singaporean woman were also injured.

Asked by State Counsel Kumaresan Gohulabalan if there was any concern about the structural integrity of the tree following the arborist's report, Mr Elango, a curator for trees, replied that there was none.

The tree was inspected twice a year, and no visual defect had been found, he said.

Asked by Senior Counsel Chelva Rajah, representing the next-of- kin, whether a decay in the tree trunk is a very serious matter, Mr Elango said it was. If it was a cavity, there could be decay.

"It could be wrongly perceived as a decay. We have to verify these things," he said.

Mr Rajah asked the basis on which he ascertained the structure was a flute. He also wanted to know if the witness had inspected it himself. Mr Elango said he and a few others did.

Mr Elango told State Coroner Marvin Bay it was impossible for a tree more than 200 years old to develop a severe defect so rapidly.

"A cavity of that length, that width, that height cannot happen over a period of one year," he said.

He said it would be of concern if it was truly a defect.

Generally, he said, tembusu trees are "heavily fluted", and it was best to check such trees.

The inquiry continues on a date to be fixed.